Conventional semiconductor devices in the form of integrated circuit chips are provided with pads for selective connection to the components of the integrated circuit, and with external connection leads that are selectively connected to the connection pads on the chip by connection wires. This whole assembly is encapsulated in a resin in such a way that only the ends of the connection leads extend outside the package. After fabricating such a semiconductor device, it is typically tested before being sold. Generally, two types of tests are performed.
A first series of tests, which are known as conduction continuity tests, is used to determine if the connection wires are cut or in contact with one another (i.e., short-circuited), and to determine if the soldered joints used for connecting the connection wires to the pads and the connection leads have been suitably produced. Typically, the connection leads are selectively connected to a current source and current flow is tested. If current does not flow, the semiconductor device is rejected. A second series of tests is used to determine if the internal circuits of the chip are operating correctly. If correct circuit operation is not observed during this testing, the semiconductor device is rejected.
In some cases, an external connection lead that is a ground connection lead is connected to two pads, which act as two ground pads for the integrated circuit. These two ground pads can act as the ground for two functionally separate parts of the integrated circuit. In such a case, the conduction continuity tests described above cannot be used for the connection wires for the single ground connection lead, which is connected to two pads on the chip. Therefore, only during the second series of tests (i.e., the functional tests) can such a semiconductor device be rejected for malfunctioning wire connections. It would be economically advantageous to be able to reject such incorrectly fabricated semiconductor devices during the first series of tests (i.e., the conduction continuity tests).